More (in)Sanity

["sundog" <sundog-at-timeship-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi all,


  Well, the 18 contact gap is done and tested.  Works like a champ
(little bit 'o vibration, but at 4k RPM's, it's bound to shake.

   I used the gap on my 9/60 and my 12/150 setups, and for the most
part, it performed very well.  On the 9/60 setup it blistered the
insulation on my primary tap a bit, and generally tended to heat up
the primary and bottom secondary turns.
  I'm running a 9/60 NST, no PFC.  A MMC of 3 strings of 13 caps
for 12.9nf.  The seconday was wound 9" with 26 gauge wire, -at-97%.
Running it at a varied breakrate, but the RMS current must have
been pretty good, because of the primary, secondary, and tank wire
heating.  I'm using 12 gauge stranded PVC insulated wire for the
tank wire.  Got quite a bit toasty. *looking at my burned thumb*
Yep, quite toasty.

  The gap worked very well, but on the 12/150 system tended to heat
up and stop working quite as well.  The sound is unbelievable, just
a good high-pitched scream. I need more current for the tank
circuit though, It'll handle a bit more ;)

  The 2x9 coil threw off ~16" sparks max, because I was using the
1.5x6 spun toroid.  I got multiple (usually 4-5) streamers of ~16".
The sparks were nice and lazy at low bps, and got frantic up to
about 700bps, where the bases would settle and become lazier, but
the ends of the streamers still went like mad.  Interesting effect.
At full speed, the 9/60 wasn't able to charge the 12nf cap up fully
between breaks, and the output dropped accordingly (down to ~11")
The sparks at high breakrates were still powerful, but weren't as
bright and vivid as the low BPS sparks. But, instead of wandering
around and taking a chance shot at a grounded object, the high BPS
sparks literally attacked their target *very* savagely.  At the end
of the run, the 2x9 coil pretty much caught fire internally, and
died.  I ran it to failure, just for giggles, and it died
sputtering sparks from halfway up the coil.  A good tough sparker
till the end.  :)

  I put the setup on the 4" coil, with much the same result, though
I was now running 12/150 for a NST farm, and the gap tended to
overheat and output would fall dramatically.  I got good solid 30"
streamers from the coil (~700-something turns of 22 ga wire), and a
6x14 toroid.  Pretty vicious sparks.

  At Dave's suggestion (and I had planned on it anyway!), I set up
my 8" form.  It's 8x23, wound with 1280 turns of 26 gauge wire.
I'd originally intended to use it as a tertiary, but it perfomred
*very* well as a secondary.  It was mis-tuned, and far undercoupled
(first secondary turn was ~4" above the primary), but it still gave
impressive sparks to the garage door (good hot ones!), and I'm
looking foward to
 (ab)using it more ;)

  A word on why I like maggies...
  Maybe they get longer sparks...They sure do drive the secondary
freq. down, needing more inductance on the primary (a Good
Thing(tm)), and can handle a *lot* of power, as the voltage is
distributed across 2 coils.  Personally, I prefer a low-inductance
driver (~200 turns or so), on a flat primary (You can still
overcouple it to destruction), and a 1000-1500 turn tertiary. Fine
wire.  It makes for a short, squat coil, that as Hull and Pool have
shown, can still blast out impressive arcs.  I like maggies 'cause
it lets me get the big-sparker out away from the primary and away
from the ground.  When the streamers get long, I have trouble with
them hitting the primary shield (polycarb. sheet).  The
low-inductance driver means you can really abuse it hard and if it
does flash over, it won't destroy it, and it's less likely to
flash.  I visualize it like hydraulics.  The driver is a big 8" low
pressure high-volume system, and you're pushing against a 1"
low-volume high pressure system.  And almost infinite pressure
available (your tank current) on the low-pressure side. A problem
on the high-pressure side is less likely to cause much havoc on the
low pressure side.  And like electricity, it's easier to move high
volume at a low pressure.  I'm probably wrong, but it simply add up
to me having *much* better results running a low inductance driver
into a high inductance tertiary than vice versa.
                Anywho, I'm off to get some work done, just wanted
to post my experience last night.  Comments, idea, and suggestions
welcome :)
                                                    Caio!
                                                    Sundog